GB332893A - Process for the manufacture of colour photographs by using photographic layers having sensitisers in colloidal solution - Google Patents

Abstract

332,893. Heide, E. Wolff-. Jan. 28, 1929. Colour photography; toning. - Photographic emulsions treated with sensitizers, such as pinacyanol, in colloidal solutions whereby a superficial layer is rendered colour sensitive, are exposed through the transparent support and after developing and fixing are treated with a solution such as a uranium intensifier until the exposed gelatine in the superficial layer has been hardened. During exposure a yellow filter may be used or the emulsion may be dyed yellow. If the superficial layer has been sensitized for red, the negative comprises a black and white, silver image formed by the blue-green light in the layer of emulsion nearest the support and a hardened gelatin,e image formed by the red light in the superficial emulsion layer. The negative is treated in a known manner with ferric ammonium oxalate, and hydrochloric acid, washed, and immersed in sodium hyposulphite solution. As a result the red values of the negative assume a transparent blue-green colour. In printing positives from the negative, the latter is immersed in a 5 per cent solution of pinatype blue D which is absorbed by the soft gelatine in the superficial image layer, and is placed in contact with the positive film under water in the dark room. The two films are then pressed together by a roller, the pinatype dye on the superficial negative image being transferred to the positive film, and are afterwards exposed to light, the black and white image on the lower layer of the negative emulsion being photographically impressed on the positive film. After developing and fixing the latter, the emulsion is hardened by a solution of alum or the blue picture is fixed by a mordant. The photographically exposed parts are coloured red by converting the silver image to a silver-uranium compound and dyeing with a basic colour, or the silver bromide picture is converted to silver iodide and then coloured. A slight yellow colour may then be applied to the total picture. A silver bromide paper with a stripping emulsion may be used as positive material. The process is similar when the superficial layer has been sensitized for green, the negative then being dyed with pinatype carmoisin red D before printing. The photographically exposed parts of t.he positive are then toned blue-green with iron ammonium alum, potassium ferricyanide, or a solution containing ferric ammonium sulphate, potassium ferricyanide oxalic acid and sulphuric acid.